The present invention relates generally to plier tools such as retaining or snap ring pliers. More particularly, the present invention relates to pliers of a type which are convertible between a first position which allows the jaws to move inwardly as the handles are moved inwardly, and a second position which allows the jaws to move outwardly as the handles are moved inwardly.
Retaining rings are utilized in annular grooves on shafts and ends of shafts to retain bearings, collars, and the like on the shaft. A retaining ring extends circumferentially between a pair of ends which have hubs. The hubs have apertures that receive tips of a plier tool. The force applied by the pliers either spreads the hubs to expand the ring or squeezes the hubs to contract the ring. The plier tool is necessary for installing the retaining ring in and removing the retaining ring from either external or internal grooves.
Accordingly, it is sometimes desirable to squeeze the handles to effect movement of the jaws outwardly to expand the ring. It is at other times desirable to squeeze the handles to effect movement of the jaws inwardly to contract the ring. Thus, it is desirable to provide a plier that is convertible between an external and an internal tool. U.S. Pat. Nos. 4,280,265 and 4,476,750 disclose a pair of retaining ring pliers that utilize a pair of separate co-planar jaws and a pair of separate handles that range about a common fixed pivot point and that are adapted to be changed to alternately engage one handle to one jaw and the other handle to the other jaw and vice versa to permit the changing of the tool from external to internal. Two fulcrum pins are disposed in the jaws and are adapted to alternately engage each set of handles to shift from a position adapted to move the jaws inwardly as the handles are moved inwardly, to a position where the jaws are moved outwardly as the handles are moved inwardly, to a position where the jaws are moved outwardly as the handles are moved inwardly.
Each of the pins disclosed in the above patents has to be independently and manually placed into the correct position. Accordingly, it may be difficult for the user of the pliers of the above patents to slide the pins into position. Accordingly, there is a need for a convertible plier tool that is easier to operate.
The present invention meets the above-described need by providing a pair of pliers capable of easily switching from a first position, suitable for internal retaining rings, wherein moving the handles inward causes the jaws to move inward to a second position, suitable for external retaining rings, wherein moving the handles inward causes the jaws to move outward.
The conversion of the tool from pliers suitable for internal retaining rings to pliers suitable for external rings is accomplished by a set of independent, coplanar jaws that are secured to rotate about a pivot. The jaws each have a slot defined therein that is disposed about the pivot. A set of handles are also independently and rotatably secured about the pivot. The handles have a pair of slots disposed on opposite sides of the pivot.
When the tool is assembled the jaws are disposed between the two handles such that the slots in the jaws and the slots in the handles are in alignment. A set of pins move up and down in the slots in the jaws such that each pin connects one handle to one jaw. The slots in the handle are disposed on each side of the pivot such that each handle can connect to either jaw by means of the pin. In this manner, each of the handles can be switched from engaging the first jaw to engaging the second jaw by manipulating the pins in the two slots. The pins are only long enough to engage one handle to one jaw. Accordingly, the movement of the pins from one end of the slot to the other end changes the engagement of the jaw from one handle to the other handle.
The motion of the pins to alternate the engagement of the handles to the respective jaws is controlled in the present invention by a set of rotating knobs that are secured to the pivot on opposite sides of the tool. The rotating knobs have a cam surface on the inside that controls a cam follower attached to a pair of bushings. The knobs are connected through the center of the tool such that turning one of the knobs causes the other knob to turn. The bushings are disposed about the pivot and each have a pin depending therefrom. The bushings are disposed adjacent to one another in a nesting fashion and are biased away from each other by a spring. The cam followers on the bushings move inward (perpendicular to the plane defined by the handles) and outward according to the cam surface in the knobs. When the cam surface in the first knob is at maximum amplitude, the pin on the bushing is driven down in the slot into engagement with the jaw and the opposite handle. When the cam surface is at minimum amplitude, the force of the spring causes the pin to engage the jaw to the handle on the same side as the knob.
Accordingly, the present invention provides for smooth operation of the pins through the cam, cam follower, and bushing. By rotating one of the knobs from a first cam position to a second cam position, the tool is changed from a pair of pliers suitable for internal retaining rings to a pair of pliers suitable for external retaining rings.
Other features and advantages of the present invention will become apparent upon reading the following detailed description of embodiments of the invention, when taken in conjunction with the accompanying drawings and the appended claims.